3.1.1 Exchange Surfaces

Question 1

what do living organisms need to keep them alive

Answer 1

oxygen, water, glucose, amino acids, minerals

Question 2

what do living organisms need to get rid of

Answer 2

carbon dioxide, urea, creatinine

Question 3

factors that affect the need for an exchange system

Answer 3

size, SA:volume, diffusion distance
metabolic rate
endotherm/ectotherm

Question 4

features of an efficient exchange surface

Answer 4

high surface area - max. molecules can diffuse per unit time
thin cell walls - short diffusion distance, faster rate
good blood supply/ ventilation - maintains steep conc. gradient
moist - enables gases to dissolve + cells protected from drying out
permeable - gases can diffuse through cell membrane

Question 5

why do smaller organisms have a lower oxygen demand

Answer 5

smaller organisms = lower metabolic activity, low demand for oxygen

Question 6

the main function of surfactant

Answer 6

lowers surface tension at the air/liquid interface within the alveoli to stop the walls from sticking together and collapsing during inhalation

Question 7

mechanism of breathing: ventilating the lungs - inspiration

Answer 7

ACTIVE
external intercostals: contract
ribs move: up and out
diaphragm: contracts
diaphragm moves: down
diaphragm shape: flattens
thorax volume: increases
thorax pressure: decreases
air: drawn in, enters
internal intercostals: relax
elastic fibres: stretch

Question 8

mechanism of breathing: ventilating the lungs - expiration

Answer 8

PASSIVE
external intercostals: relax
ribs move: down and in
diaphragm: relax
diaphragm moves: up
diaphragm shape: domed
thorax volume: decreases
thorax pressure: increases
air: expelled, leaves
internal intercostals: relax
elastic fibres: recoil to expel air

Question 9

cartilage is found in

Answer 9

trachea - c-shaped rings
bronchus - plates

Question 10

goblet cells are found in

Answer 10

trachea
bronchus

Question 11

ciliated cells are found in

Answer 11

trachea
bronchus
bronchioles

Question 12

smooth muscle is found in

Answer 12

trachea
bronchus
bronchioles

Question 13

elastic fibres are found in

Answer 13

trachea
bronchus
bronchioles
alveolus

Question 14

squamous epithelium is found in

Answer 14

alveolus

Question 15

function of cartilage

Answer 15

strong - prevents collapse of trachea and bronchus
flexible- trachea and bronchi bend/extend
c-shaped rings - oesphagus can expand behind

Question 16

function of goblet cells

Answer 16

secrete mucus- contains glycoproteins, traps pathogens

Question 17

function of ciliated cells

Answer 17

hair like projections beat to waft mucus up the airway

Question 18

function of smooth muscle

Answer 18

contracts - constricts/ narrows airway e.g. if there is a harmful substance in the air
relaxes - dilate airway to increase air flow to alveoli

Question 19

function of elastic fibers

Answer 19

bronchioles- when smooth muscle contracts, elastic fibers stretch. when smooth muscle relaxes, elastic fibers recoil
alveoli- stretch to allow alveoli to expand. recoil to expel air. prevents bursting during inhalation

Question 20

function of squamous epithelium

Answer 20

thin, flattened cells - short diffusion distance = increased rate of gaseous exchange

Question 21

why is a nose clip worn when using a spirometer

Answer 21

to prevent the subject from breathing via the nose

Question 22

how does a spirometer work

Answer 22

breathe out into tank - upper half rises
breathe in from tank - upper half falls
a tracemarker is attached to mobile upper half connected to kymograph which records changes in oxygen

Question 23

why does total volume in tank slowly decline

Answer 23

the subject uses up oxygen from tank due to gas exchange in alveolus - left in dead space

Question 24

why is soda lime used in spirometer

Answer 24

soda lime absorbs carbon dioxide that is exhaled

Question 25

why does exhaled air contain oxygen

Answer 25

some inhaled air does not reach the alveolus for gas exchange to occur

Question 26

tidal volume

Answer 26

volume of air that flows in and out of the lungs with each breath during quiet breathing - usually measured at rest

Question 27

vital capacity

Answer 27

maximum volume of air that can be moved by the lungs in one breathe strongest possible exhalation followed by strongest possible inhalation

Question 28

inspiratory reserve volume

Answer 28

maximum amount of air inspired in excess of the tidal volume - a normal inhalation

Question 29

expiratory reserve volume

Answer 29

maximum amount of air expired in excess of the tidal volume

Question 30

residual volume

Answer 30

volume left in lungs after maximum forced expiration

Question 31

total lung capacity

Answer 31

total air in lungs after maximum inhalation total volume lungs can hold

Question 32

total air breathed per minute

Answer 32

tidal volume x breathing rate

Question 33

how might athletic training affect the condition of the lungs

Answer 33

more efficient lungs - improved network of pulmonary capillaries so more oxygen is taken up slightly increases lung volume increase in alveoli size increased strength in muscles - can breathe in more air for longer periods of time faster breathing rate - more oxygen produced higher tidal volume

Question 34

why do fish have an exchange system

Answer 34

**multicellular, move around:** fairly high metabolic rate **ectotherms:** cannot increase metabolic rate to maintain temperature, lower oxygen demand **fairly large - small SA:V ratio:** large diffusion distance so cannot rely on simple diffusion alone **water is thicker + denser than air: **more energy req. to cross gas exchange surfaces

Question 35

structure of fish gills in bony fish

Answer 35

series of gills on each side of the head each gill arch attaches to 2 rows of filaments, 1 row of gill rakers rows of lamellae in filaments lamellae surface consists of a single layer of flattened cells that cover a vast network of capillaries

Question 36

gill rakers

Answer 36

made of bone or cartilage prevents food particles reaching filaments prevents obstruction of gas exchange

Question 37

how does the structure of the gills relate to their function

Answer 37

**lots of filaments/lamellae:** provide large SA **filaments + lamellae have thin walls:** short diffusion distance filaments + lamellae increase rate of diffusion of oxygen and carbon dioxide **filament tips overlap:** increases resistance to flow of water = gives time for diffusion of gases **good blood supply via capillary network in capillaries in lamellae:** maintains steep concentration gradient **counter current flow of blood and water:** maintains concentration gradient across full length of gill

Question 38

counter current system of blood and water flow

Answer 38

blood and water flow in opposite directions ensures concentration of oxygen in water is always higher than concentration of oxygen in the blood concentration gradient can be maintained more oxygen will diffuse into the blood

Question 39

ventilation in a bony fish: inspiration

Answer 39

mouth opens, operculum closed buccal cavity floor lowers (muscles req. - ATP) buccal cavity: pressure decreases, volume increases water flows in via mouth down a pressure gradient sides of opercular cavity bulge outwards (muscles req. - ATP) opercular cavity: pressure decreases, volume increases mouth closes, buccal cavity floor rises buccal cavity: volume decreases, pressure increases pressure in buccal cavity > pressure in opercular cavity water forced to flow over gills, down pressure gradient

Question 40

ventilation in a bony fish: expiration

Answer 40

sides of opercular cavity move inwards operculum opens water flows in one direction over gills and is expelled

Question 41

why do insects have an exchange system

Answer 41

**fairly active + multicellular:** certain oxygen demands **tough exoskeleton:** impermeable to gases no exchange via skin **small - large SA:V ratio: ** short diffusion distance, can rely on simple diffusion

Question 42

tracheal system of an insect

Answer 42

**spiracle:** allows air to enter the insect **tracheae:** have rigid rings of cartilage to keep it open **muscle fibres:** the site of gas exchange

Question 43

function of tracheae

Answer 43

held open byb citin enables carbon dioxide and oxygen to diffuse down

Question 44

function of trachioles

Answer 44

lots of trachioles increases SA moist lining for gases to dissolve lots of tracheal fluid at the end of trachiole which oxygen diffuses through

Question 45

when insects are active

Answer 45

muscles anaerobically respire to produce lactic acid decreases water potential - drawing tracheal fluid into muscles by osmosis more air is drawn in higher surface area of the walls exposed for diffusion rate of diffusion increases